The present invention relates to a roll damper arrangement for a motor vehicle.
It is known, for example from GB 2275661 to provide a rotary damper operating between the two halves of a split anti-roll bar so as to damp roll movements of a vehicle. However this type of arrangement can have disadvantages, particularly for off-road vehicles where large degrees of axle articulation are required and a high degree of roll damping, which is desirable on-road, can reduce the ability of the axles to articulate as required.
It is therefore an aim of the present invention to provide a roll control system which can provide the roll control required on-road and the articulation required off-road.
Accordingly the present invention provides a roll damper apparatus for a motor vehicle having two wheels on opposite sides thereof, the apparatus comprising a first member defining a cavity and a second member located within said cavity to divide the cavity into two chambers, wherein at least one passage is defined between the chambers, the cavity contains fluid, and the first and second members are connected between said wheels such that roll of the vehicle will cause movement of the second member relative to the first, such movement being damped by the flow of fluid through said at least one passage, the second member having a central position corresponding to a level condition of the wheels, and said at least one passage being arranged to increase in effective cross sectional area as the second member moves to either side of the central position such that roll damping decreases.
The increase in effective cross sectional area can be achieved by increasing the cross sectional area of at least one of the passages, or by increasing the number of said passages which are open, or both.
It can also be a problem with current systems which include anti-roll bars and roll dampers that the packaging is difficult. It is therefore a further aim of the present invention to provide such a system which is relatively compact.
Accordingly the present invention further provides a roll control apparatus for a vehicle having two wheels on opposite sides thereof of, the apparatus comprising an anti-roll torsion bar connected between said wheels so as to produce torsional resistance to roll movement of the vehicle, and a damper comprising a stator defining a cavity and a rotor located within said cavity to divide the cavity into two chambers, wherein a passage is defined between the chambers, the cavity contains fluid, such movement being damped by the flow of fluid through the passage, and the rotor and stator are mounted around the torsion bar and connected to the wheels via connecting means so that they provide damping resistance to vehicle roll in parallel to the torsional resistance of the torsion bar.
It can be a problem with known rotary dampers, such as that shown in EP 0 524 607 that air in the working chambers can build up, affecting the damping characteristics.
The present invention further provides a roll damper apparatus for a motor vehicle having two wheels on opposite sides thereof movable into and out of a level condition, the apparatus comprising a first member defining a cavity and a second member located within said cavity to divide the cavity into two chambers, wherein a passage is defined between the chambers, the cavity contains fluid, and the first and second members are connected between the wheels such that vehicle roll will cause movement of the second member relative to the first, such movement being damped by the flow of fluid through the passage, the second member having a central position corresponding to the level condition of the wheels, wherein the first member at least partly defines a bleed path arranged to allow bleeding of at least one of fluid and air out of the cavity, the bleed path opening into the cavity at a point aligned with the central position of the second member.
This allows the provision of a bleed path which does not adversely affect the characteristics of the damper.
The present invention also aims to provide a damper which is cheap and simple to manufacture.
Accordingly the present invention still further provides a roll damper apparatus for a motor vehicle having two wheels on opposite sides thereof, the apparatus comprising a plurality of stator members each at least partly defining a respective cavity and a plurality of rotor members each located within a respective one of said cavities to divide it into a pair of chambers, wherein a passage is defined between each pair of chambers, the cavities contain fluid, and the rotor and stator members are connected to said wheels such that vehicle roll will cause movement of the rotors relative to the stators, such movement being damped by the flow of fluid through the passages, wherein the apparatus further comprises support members and a spring and the rotor and stator members comprise plates slidably mounted on the support members and clamped in position by means of the spring.